The invention relates to a lock for a vacuum chamber which lock has a passage comprising an outer sealing means and an inner sealing means which outer sealing means can be maintained in the closed position under the influence of the pressure difference caused by the vacuum in the vacuum chamber, and can be opened against the force caused by said pressure difference, which inner sealing means under pretension can be maintained in the opened position and comprises closing means for closing the inner sealing means against said pre-tension.
By means of such a lock products can be transferred between the inner space of the vacuum chamber and the surrounding thereof, namely in such a manner that the vacuum is maintained. In the vacuum chamber various operations can be performed onto the product. More specifically one may think of applying a metal layer by means of a sputtering operation onto a substrate such as a CD-disc or DVD-disc.
In the known lock the inner sealing means is maintained in the closed position in a mechanical manner. Therefore, a pushing rod has to be applied which has to be operated from the outside through the wall of the vacuum chamber. Such a way of handling will lead to problems, which can influence the operation of the vacuum manner in a disadvantageous way. It appears not to be easy to displace the inner sealing means plan parallel in the correct way such that the required seal is indeed obtained for maintaining the vacuum. A further problem is that the seal of the pushing rod in relation to the wall of the vacuum chamber cannot always be maintained.
Object of the invention is now to provide a lock of the above-mentioned type, which does not have said disadvantages. Said object can be reached in case the closing means do comprise an electromagnet.
By means of the electromagnet the inner sealing means can be operated without the necessity of a mechanical transfer through the wall of the vacuum chamber. Therefore, sealing problems are eliminated. Furthermore the required parallel movement of the inner sealing means is obtained by the co-operation of the electromagnet with for instance a pole piece. For that purpose the electromagnet may extend around said passage and the pole piece may extend over the inner sealing means in a corresponding way. Especially the passage and the outer and inner sealing means can be cylindrical.
To improve the co-operation between the electromagnet and the pole piece, the pole piece has at the surface directed to the electromagnet least one annular ridge or groove, and the area around the passage has at least a correspondingly situated groove respectively ridge, which ridge can be inserted into said groove in case the passage is closed by means of the inner sealing means. The ridge and groove will take care for a correct mutual positioning of the inner sealing means and the passage.
Instead of a pole piece also a second electromagnet or permanent magnet can be provided.
The outer sealing means comprises an annular O-seal, which under the influence of the vacuum is maintained pressed on, the inner sealing means has an annular O-seal which under the influence of the activated electromagnet can be maintained pressed on.
The invention furthermore relates to a vacuum chamber, such as a sputter device, comprising at least one lock, which lock has a passage comprising an outer sealing means and an inner sealing means, which outer sealing means can be maintained in the closed position under the influence of the pressure difference caused by the vacuum in the vacuum chamber and can be maintained opened against the force generated by said pressure difference, which inner sealing means can be maintained in the open position under pretension and comprises locking means for closing the inner sealing means against said pretension, which vacuum chamber comprises a table, which table is displaceable along the passage and carries said inner sealing means. The closing means do comprise an electromagnet and a pole piece, a second electromagnet or a permanent magnet.
In a preferred embodiment said vacuum chamber comprises a drum-shaped housing with cylindrical surrounding wall as well as two walls at both ends of said cylindrical surrounding wall in one of which a cylindrical passage is made with an outer vacuum cap, in which housing a table with circular surrounding is mounted in a coaxial rotatable manner.